Coastal ocean variability in the US Pacific Northwest region: seasonal patterns, winter circulation, and the influence of the 2009–2010 El Niño
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A 2-km horizontal resolution ocean circulation model is developed for a large coastal region along the US Pacific Northwest (34–50N) to study how continental shelf, slope, and interior ocean variability influence each other. The model has been run for the time period September 2008–May 2011, driven by realistic surface momentum and heat fluxes obtained from an atmospheric model and lateral boundary conditions obtained from nesting in a global ocean model. The solution compares favorably to satellite measurements of sea surface temperature and sea surface height, observations of surface currents by high-frequency radars, mooring temperature time series, and glider temperature and salinity sections. The analysis is focused on the seasonal response of the coastal ocean with particular emphasis on the winter circulation patterns which have previously garnered relatively little attention. Interannual variability is examined through a comparison of the 2009–2010 winter influenced by El Niño and the winters in the preceding and following years. Strong northward winds combined with reduced surface cooling along the coast north of Cape Mendocino (40.4N) in winter 2009–2010, resulting in a vigorous downwelling season, characterized by relatively energetic northward currents and warmer ocean temperatures over the continental shelf and upper slope. An analysis of the time variability of the volume-averaged temperature and salinity in a coastal control volume (CV), that extends from 41 to 47N and offshore from the coast to the 200-m isobath, clearly shows relevant integrated characteristics of the annual cycle and the transitions between winter shelf circulation forced by northward winds and the summer circulation driven primarily by southward, upwelling-favorable winds. The analysis also reveals interesting interannual differences in these characteristics. In particular, the CV volume-average temperature remains notably warmer during January–March 2010 of the El Niño winter.
KeywordsCoastal ocean variability El Nino Coastal ocean modeling Northeast Pacific Downwelling
This research was supported by the National Science Foundation (NSF, grants OCE-1030922, OCE-0527168 and OCE-0961999), the National Aeronautics and Space Administration (NASA, grant NNX13AD89G), and the National Oceanic and Atmospheric Administration (NOAA), through the Coastal Ocean Modeling Testbed (COMT) program and the Northwest Association of Networked Ocean Observing Systems (NANOOS), the Regional Association of the national Integrated Ocean Observing System (grant NA11NOS0120036).
- Adams KA, Barth JA, Chan F (2013:) Temporal variability of near‐bottom dissolved oxygen during upwelling off central Oregon, J. Geophys. Res. Oceans, 118, doi: 10.1002/jgrc.20361
- Bjorkstedt EP, Goericke R, McClatchie S, Weber E, Watson W, Lo N, Peterson P, Emmett B, Peterson J, Durazo R, Gaxiola-Castro G, Chavez F, Pennington JT, Collins CA, Field J, Ralston S, Sakuma K, Bograd S, Schwing F, Xue Y, Sydeman W, Thompson SA, Santora JA, Largier J, Halle C, Morgan S, Kim SY, Merkens J, Hildebrand J, Munger L (2010) State of the California current 2009–2010: regional variation persists through transition from La Niña to El Niño (and back?). Calif Coop Oceanogr Fish Investig Rep 51:39–69Google Scholar
- Donlon CJ, Martin M, Stark J, Roberts-Jones J, Fiedler E, Wimmer W (2012) The Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) system. Remote Sens Environ 116:140–158Google Scholar
- Kalnay R, Kanamitsu M, Kistler R, Collins W, Deaven D, Gandin L, Iredell M, Saha S, White G, Woollen J, Zhu Y, Leetmaa A, Reynolds R, Chelliah M, Ebisuzaki W, Higgins W, Janowiak J, Mo KC, Ropelewski C, Wang J, Jenne R, Joseph D (1996) The NCEP/NCAR 40-year reanalysis project. Bull Am Meteorol Soc 77:437–471CrossRefGoogle Scholar
- Kim SY, Kosro PM, Kurapov AL (2014) Evaluation of directly wind-coherent near-inertial surface currents off Oregon using a statistical parameterization and analytical and numerical models, J. Geophys. Res. in pressGoogle Scholar
- Mazzini PLF, Barth JA, Shearman RK, Erofeev A 2014 Buoyancy-driven coastal currents off the Oregon coast during fall and winter. J. Phys. Oceanogr. In pressGoogle Scholar
- Sutherland DA, MacCready P, Banas NS, Smedstad LF (2011) A modeling study of the Salish Sea estuarine circulation. J Phys Oceanogr 1125–1143Google Scholar
- Walters HM (2014) Relationship between winter downwelling and conditions and summer hypoxia severity along the Oregon coast. BSc Thesis, Oregon State Univ, p 40Google Scholar